Road widening in curves according to the Croatian regulations, German guidelines and the computer simulation of vehicle movement

Stančerić, Ivica; Tomić, Iris; Bezina, Šime; Džambas, Tamara · 2021 · Crossref

DOI: 10.5592/co/cetra.2020.983

archive: archived pipeline: cataloged verified

Get this paper ↗ (DOI — opens at the source; we link to it, we don't host it)

Summary

This study addresses the determination of road widening requirements in horizontal curves, a necessary design feature because the rear wheels of vehicles follow a trajectory with a smaller radius than the front wheels. The research compares widening values derived from Croatian regulations and German guidelines against those obtained through computer simulation of vehicle movement. The motivation is to evaluate the accuracy and safety implications of existing regulatory formulas, particularly for long design vehicles such as trucks with trailers, semi-trailer trucks, and buses. The methodology involved calculating required widening for circular arcs with radii ranging from 12.5 to 500 meters and turning angles from 45 to 270 degrees. Croatian regulations use specific formulas based on vehicle type (e.g., $\Delta s = 42/R$ for trucks with trailers), while German guidelines apply a single formula ($i = 100/R$) for curves with radii under 200 meters. These calculated values were compared against simulations performed using Autodesk Vehicle Tracking software. The study selected three specific design vehicles: a 15.0-meter three-axle bus, a 16.5-meter semi-trailer truck, and an 18.75-meter truck with a trailer. A total of 162 combinations of radii, turning angles, and vehicle types were processed to analyze the relationship between regulatory requirements and simulated vehicle trajectories. The results indicate significant discrepancies between the regulatory approaches and simulation data. The Croatian formula for trucks with trailers yields smaller widening values than the German guideline formula and is only applicable for curve radii greater than 25 meters. Conversely, the German guideline formula produces higher widening values than the simulation results for both truck types across all radii greater than 25 meters, suggesting a conservative safety margin. The simulation revealed that the three-axle bus occupies the largest surface width across all tested radii and turning angles. The maximum widening requirement occurred at a 270-degree turning angle with a 12.5-meter radius. Furthermore, the influence of the turning angle on required widening was found to be most significant for curves with radii less than 45 meters. The study concludes that German guidelines correspond more closely to real vehicle movement patterns than Croatian regulations, although they tend to overestimate widening needs for trucks. The findings highlight that for curve radii smaller than 45 meters, widening must be determined based on specific vehicle movement trajectories due to the high sensitivity to turning angles. Additionally, the research suggests that no widening is required for curve radii greater than 250 meters if the non-widened roadway width is 3.00 meters, or greater than 120 meters if the width is 3.50 meters. These insights underscore the need to update existing regulations to better reflect actual vehicle dynamics and optimize road design safety.

Provenance

The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed.

Summary generated by qwen3.6-27b-prismaquant on 2026-06-26; verification: verified.

Topics

Ranked by relevance to this paper. Hover a topic for its definition.

• road geometry